Biased agonism in psychopharmacology: an opportunity to improve efficacy and safety of treatments.

Summary

G protein-coupled receptors (GPCRs) are involved in many bodily processes. Traditional drug classification divides ligands into agonists or antagonists. Biased agonism is a newer concept where a drug selectively activates one intracellular signaling pathway over another, such as G protein versus β-arrestin pathways. This narrative review of literature up to April 2025 describes distinct mechanisms of antagonism and agonism beyond conventional models. Biased agonism has shown potential for greater efficacy, as with the incretin receptor agonist tirzepatide, and improved safety, as with certain serotonergic psychedelics and opioids. Preclinical evidence suggests biased agonism could improve psychiatric and neurological treatments by differentially activating pathways, pending clinical validation.

Study at a glance

Abstract

G protein-coupled receptors (GPCRs) are involved in many physiological and pathophysiological processes. Conventional pharmacological models categorize the typology of pharmacologic ligands as agonists or antagonists. Biased agonism is a relatively newer pharmacodynamic characteristic that has potential to optimize therapeutic efficacy while minimizing adverse effects in psychiatric and neurological treatments. We conducted a narrative literature review of articles obtained from PubMed, Embase, and MEDLINE from inception to April 2025, focusing on pharmacologic antagonism (i.e., competitive, noncompetitive, uncompetitive) and agonism (i.e., full, partial, inverse, superagonism, biased). Primary and secondary articles defining these concepts were included, provided they addressed pharmacologic (rather than chemical) antagonism and agonism. Distinct mechanisms of antagonism and agonism were identified, each contributing nuanced receptor modulation beyond the conventional models. Notably, biased agonism facilitates targeted intracellular signaling (e.g., G protein- versus β-arrestin-mediated). Use cases demonstrate relatively greater efficacy (e.g., incretin receptor agonist, tirzepatide) and improved safety (e.g., serotonergic psychedelics, opioids). Biased agonism provides a potential avenue for future drug development, with emerging preclinical evidence suggesting potential to differentially activate intracellular pathways and thereby improve efficacy and safety profiles of psychopharmacologic agents-pending clinical validation. Future research vistas should aim to rigorously assess the long-term outcomes of biased agonism, explicitly addressing individual variability in receptor signaling and therapeutic response.